Growing wine grapes in Minnesota on a commercial scale is a relatively new endeavor because the region's mid-continental climate yields exceptionally cold winters that create challenges for the emerging wine industry. At the same time, the cold climate in Minnesota creates opportunities for the production of Ice Wine, which is made from grapes frozen on the vine in the traditional German style. The freezing and thawing of the grapes dehydrates the fruit, concentrates the sugars and acids, and extracts flavors in the berries, thereby intensifying the flavors and adding complexity to the wine made from it. A rare delicacy in the wine world, Ice Wine is becoming increasingly rare as traditional winegrowing regions have experienced warmer temperatures than average during recent years.
At present, less than 30 wineries exist in Minnesota, extending from southern Minnesota to just south of the Canadian border. Many of these wineries produce non-grape wines from honey, rhubarb, raspberries, and the other fruit. However, several Minnesota wineries are currently managing substantial vineyard tracts. A few wineries have even received awards for wines produced by these vineyards at top international wine competitions. However, production of Ice Wine in Minnesota remains difficult because many known grapevine varieties have a tendency for their fruit to split and fall from the cluster after a hard freeze.
Despite some success, grape growing in Minnesota is fraught with difficulties. Most European grape varieties that are grown in Minnesota, and even many “French-American hybrid” wine varieties, require protection if they are to survive the frigid winters—especially in northern Minnesota. This is usually done by removing vines from the trellises and bending them to the ground in early November, then covering the vine with soil or straw.
Although covering vines effectively insulates them from cold winter temperatures, there are a number of problems that make this practice less than satisfactory. Of primary concern is the greatly increased labor cost, which is generally prohibitive and makes it quite difficult for Minnesota vineyards to operate profitably. However, logistical challenges exist as well. For example, the trunks of the vine may break due to the fact that they become less pliable as they grow larger in diameter. If the vine does not break, fungi and bacteria may infiltrate the vine through small “stress cracks” in the trunk, causing disease. Rodents commonly feed on the trunks and canes as they lay on the ground during the winter, further injuring the vine. If the vine survives the winter, great care must be taken to avoid damaging the buds when the vines are uncovered during the spring. Accordingly, for grapevines to be of high commercial value to vineyards in northern regions, it is nearly essential for varieties to be hardy enough to remain on the trellises throughout the winter months without removal and winter covering.
Fortunately, there exist good sources of tolerance to cold hardiness for breeding purposes, i.e. Vitis riparia and Vitis labrusca. These hardy grapes have a flavor that is acceptable in table wines. However, they are too high in acid and too unproductive to use on their own.
Some of the hardiest known wine grape varieties, ‘Sabrevois’ (ES 2-1-9), and ‘Frontenac’ (MN 1047), have demonstrated hardiness to at least −35 degrees F. (about −37.2 degrees C.) in Chisago City, Minn. A relatively new variety, the ‘Chisago’ grape (U.S. Plant Pat. No. 19,246) has been shown to be winter hardy to about −40 degrees F. (about −40 degress C.). At this location, the present variety has proven that it is at least as winter hardy as these known varieties. The present variety also presents a wide variety of additional distinguishing characteristics including vigor, productivity, resistance to disease and pests, size of fruit, size of grape clusters, coloration, and flavor, ability to retain cluster integrity and resist cracking after a freeze, hereinafter set forth in detail.